This is a continuing study designed to (1) appraise the role of thyrotropin in the genesis, growth and progression of thyroid cancers, (2) develop improved methods of differentiating thyroid cancer from benign adenoma, adenomatous goiter, cysts, subacute and chronic thyroiditis, (3) evaluate the role of suppressive therapy in the management of nodular goiters and thyroid cancers, and (4) study factors influencing survivorship in thyroid cancer by means of a specifically designed computer program. These objectives will be pursued via a systematic appraisal of patients with thyromegaly, using scanning techniques, sonography, suppressive therapy and needle biopsy to differentiate benign from malignant disease. By continued evaluation of all patients with thyroid cancer, factors influencing survivorship, i.e., TSH-TH levels, age, sex, histopathologic characteristics (light and electron microscopy), extent of disease and types of treatment, will be studied.